This invention relates to liquid pumps, and more particularly, to an improved flow inducer arrangement for double or tandem seals in a liquid pump.
In liquid pump assemblies which employ double or tandem seals, a buffer fluid must be circulated between the two seal faces to maintain proper lubrication. In known systems, a reservoir containing a suitable fluid is communicated with the interior of the pump to supply the fluid to the mating or opposing seal faces. Typically, the capacity of the reservoir varies from one quart to five or more gallons. To assure circulation and thereby avoid overheating of the seals and the fluid, various approaches have been tried. In one approach, which is commonly referred to as thermo syphon, the outlet of the reservoir is communicated with the seal cavity permitting the lubricating fluid to be drawn into the seal cavity and moved therethrough. This arrangement has not proven satisfactory because of the small and uncertain flow conditions provided, particularly when the liquid in the main pump is a volatile fluid. In such case, gas can be forced into the seal cavity resulting in air or vapor bind in the thermal-syphon circulation path.
Another attempt at avoiding overheating of the seals and lubricating fluid is the use of agitation of the seal rotary units. However, this arrangement does not provide sufficient differential pressure to assure that circulation of the lubricating fluid through the seal cavity is maintained.
Another arrangement which is employed uses a "pumping ring" or impeller with radial or spiral notches which is located within the seal cavity and rotated, drawing lubricating fluid into the seal cavity. However, this arrangement does not include a means to contain the fluid and direct its flow and thus does not achieve adequate differential pressure to maintain the required circulation of the liquid through the seal cavity.
Therefore, it would be desirable to have a circulation system which is constructed and arranged to contain the lubricating fluid and direct its flow so as to avoid overheating of the seals and of the fluid.